Liquid crystal display device

ABSTRACT

The invention relates to a liquid crystal display device ( 1 ) with a negative display when no current is supplied. Said device comprises a liquid crystal layer that is built into an active zone ( 2 ) between substrates, the exterior of each of said substrates being covered by pole filters that are aligned in an arrangement for the currentless negative display. The interior of said substrates is provided with segments ( 2.2 ) of surface electrodes that are separated from one another by means of electrically insulating dividing lines ( 5 ), said segments being connected to connection lines that lead to the exterior. Masking is provided on the interior of the substrate for areas that would otherwise remain bright during retrace blanking. The invention provides an advantageous construction and display quality, as the periphery of the active zone ( 2 ) is encompassed by adhesive strips ( 4 ), which appear black, between the substrates, and the masking, at least in bright areas that would otherwise be visible from a conventional viewing distance during retrace blanking, is produced by means of additional adhesive strips ( 4 ′).

[0001] The invention relates to a liquid crystal display device, which in the voltageless state is bright, having a liquid crystal layer placed in an active zone between substrates, the substrates each being covered on the outside by pole filters oriented in an arrangement for the voltageless bright display and on their inside carrying segments of surface electrodes, the segments being separated from one another by electrically insulating dividing lines, which segments are connected to connection lines leading to the outside, and masking for areas that otherwise remain bright in retrace blanking being provided on the inside of the substrate.

[0002] One such liquid crystal display device is disclosed in U.S. Pat. No. 4,952,030. Such liquid crystal display devices for generating displays that are bright in the voltageless state have the advantage, over displays that are dark in the voltageless state, that the dark activated areas of the cells do not appear in color but instead are correctly black. The bright areas that are not activated are equally bright for light from all directions; thus the incident light is better utilized than in cells that are dark when voltageless. The displays that are bright when voltageless can also be produced markedly less expensively, among other reasons because the dark background does not appear in color as a function of the viewing angle, and complicated countermeasures need not be taken to achieve a uniform color. In the cell that is bright when voltageless, the optical axes of the two polarization sheets are crossed. The non-activated areas are always bright, while the activated segments are conversely black. Thus even the region of the edge of the adhesive that encloses the liquid crystal area appears black. The aforementioned patent teaches possible ways, in the case of displays that are bright when voltageless, of being able to display bright segments on a dark background with good contrast and in particular even with an oblique viewing angle, for instance from a lower half-space. To that end, a twisting angle of the liquid crystal layer of <90° and in particular of 50° to 80° is recited. However, in such displays that are bright when voltageless, it is difficult to cause the bright non-activated areas to appear dark. For that purpose, the bright areas are covered with a light-absorbing mask, which to avoid parallax is usually placed on the inside of the substrate, as recited in U.S. Pat. No. 4,952,030. Masking is an expensive, complicated additional step in production.

[0003] A further liquid crystal display device for generating displays that are bright in the voltageless state is shown in German Patent Disclosure DE 37 82 916 A1; once again, a twisting angle of the liquid crystal layer of <90° is recited, for achieving favorable viewing from an oblique direction to the normal.

[0004] The object of the invention is to furnish a liquid crystal display device which with a simplified design produces the best possible display properties, and in particular even for relatively large displays.

[0005] This object is attained with the characteristics of claim 1. It is accordingly provided that the active zone is surrounded on the periphery with adhesive strips that appear black between the substrates; and that the masking is produced, at least in bright areas that at the conventional viewing distance are clearly visible is produced by means of further adhesive strips.

[0006] With these provisions, the masking is accomplished with the same material and in the same production step as making the outlining of the active zone and the adhesive bonding of the two substrates. As a result, there is a marked reduction in production costs and a stable design of the display device. In this embodiment, the fact that in displays that are bright when voltageless all the areas in which there is no liquid crystal appear black is exploded; this is also true for those areas in which the adhesive is located. By application using adhesive pressure, the adhesive can be applied exactly and in an easily predetermined manner in areas to be masked within the cell during production. The result is a malfunction-free display, which in conjunction with a liquid crystal with a twisting angle of <90° is preferably advantageous even for oblique viewing, for instance from a lower half-space.

[0007] One advantageous feature for the structure and realization of the display is that the further adhesive strips are disposed at least in the region of the connection lines.

[0008] Further advantageous provisions for the structure and realization of the display are obtained by providing that the active zone is rectangular or square in shape, and the further adhesive strips are disposed continuously parallel to an outside, at equal spacings, for forming subsidiary regions in the form of rows or columns. A favorable design is that a plurality of connection lines are placed jointly in the region of the further adhesive strips.

[0009] An advantageous arrangement is moreover achieved by providing that the rows or columns are subdivided into a plurality of equal-size square or rectangular subgroups of segments, each including at least one segment.

[0010] For a simple line course and thus the simple structure, the provisions that each segment adjoins one adhesive strip or further adhesive strips, which cover connection lines are also favorable.

[0011] The provisions that a peripheral side is interrupted, for introducing the liquid crystal, in the region of an adhesive strip meeting it at a right angle, and that each thus-formed introduction opening leads to two subsidiary regions located side by side, contribute to simple production.

[0012] The invention is described in further below in terms of exemplary embodiments in conjunction with the drawings. Shown are:

[0013]FIG. 1, a schematic illustration of a liquid crystal display device in a front view, with a plurality of display segments and adhesive pressure applied; and

[0014]FIG. 2, a schematic illustration of the liquid crystal display device with the adhesive pressure of FIG. 1.

[0015]FIG. 1 shows a liquid crystal display device 1, with an active zone 2 which is subdivided into a plurality of subsidiary regions in the form of columns 2.1 and which is demarcated by a surrounding region 3 for an outer boundary by means of adhesive strips 4 between substrates on both sides. In the interior of the active zone 2, for an inner boundary, the columns 2.1 are demarcated from one another between the substrates on both sides by means of further adhesive strips 4′. Many segmented surface electrodes (in the present case, 38 of them) in the form of segments 2.2 are formed, on the sides toward one another of the substrates on both sides, by means of thin insulating dividing lines 5, in order to activate a liquid crystal, introduced into the active zone 2 between the substrates via introduction openings 7 in a desired manner.

[0016] In FIG. 2, the adhesive strips 4 serving as an outer boundary of the active zone 2 and the further adhesive strips 4′ serving as an inner boundary of the columns 2.1 are shown without the dividing lines 5 for the sake of clarity. For venting the surrounding region 3, vent openings 6 are provided.

[0017] The liquid crystal display device 1 is covered, as is conventional per se, on the outside of the substrate with polarization filters, which for a display that is bright when voltageless are disposed with their directions of polarization opposite one another. For viewing at an angle oblique to the normal, and in particular from a lower half-space, for instance, as is often the case in looking at large displays, suitable provisions are made, as in the prior art cited at the outset (DE 37 82 915 A1 and U.S. Pat. No. 4,952,030); that is, in particular, a liquid crystal with a twisting angle <90° is used.

[0018] For simple introduction of the liquid crystal via the introduction openings 7, the further adhesive strips 4′ that demarcate the columns 2.1 are disposed with one end of each of them approximately centrally in the introduction opening 7, making simple introduction of the liquid crystal into the region of the columns 2.1 and subsequently simple closure possible.

[0019] The adhesive strips 4 and the further adhesive strips 4′ are applied by means of adhesive pressure to the appropriate points on the inside between the two substrates, before they are joined together in production, and form masking that appears black from outside for places that would otherwise appear bright. The adhesive bonding of the two substrates and the masking are thus applied with the same adhesive in one production step by means of adhesive pressure. The fact that in areas that are bright when voltageless, all the areas in which there is no liquid crystal appear black is exploited here. This is also true for the areas in which the adhesive is located.

[0020] The supply lines, leading to the outside, of transparent conductive material (ITO) to the individual segments 2.2 in the cell extend in the dividing strips between the columns 2.1 and in the areas outside the active zone 2. The adhesive strips 4 and the further adhesive strips 4′ cover these areas that otherwise appear bright, so that the strips appear black. The adhesive strips 4 closely surround the active zone 2. The supply lines furnish a connection between terminals 8 and the segments 2.2. The dividing lines 5, produced by etching, between the segments 2.2 can be kept very slender (for instance <0.1 mm) so that particularly when the display is viewed from the usual relatively great distance, these dividing lines are not in the way.

[0021] Via the vent openings 6, the surrounding region 3 outside the active zone 2 is vented during production. It is sealed once the adhesive has cured.

[0022] With the provisions described, both a simple structure and stable liquid crystal display device with unimpeded display when it has displays that are bright when voltageless is obtained, which is advantageous in particular for high-contrast oblique viewing, for instance from a lower half-space. 

1. A liquid crystal display device (1), which in the voltageless state is bright, having a liquid crystal layer placed in an active zone (2) between substrates, the substrates each being covered on the outside by pole filters oriented in an arrangement for the voltageless bright display and on their inside carrying segments (2.2) of surface electrodes, the segments being separated from one another by electrically insulating dividing lines (5), which segments are connected to connection lines leading to the outside, and masking for areas that otherwise remain bright in retrace blanking being provided on the inside of the substrate, characterized in that the active zone (2) is surrounded on the periphery with adhesive strips (4) that appear black between the substrates; and that the masking is produced, at least in bright areas that at the conventional viewing distance are clearly visible is produced by means of further adhesive strips (4′).
 2. The device of claim 1, characterized in that the further adhesive strips (4′) are disposed at least in the region of the connection lines.
 3. The device of claim 1 or 2, the active zone (2) is rectangular or square in shape, and the further adhesive strips (4′) are disposed continuously parallel to an outside, at equal spacings, for forming subsidiary regions (2.1) in the form of rows or columns.
 4. The device of claim 3, characterized in that a plurality of connection lines are placed jointly in the region of the further adhesive strips (4′).
 5. The device of claim 3 or 4, characterized in that the rows or columns (2.1) are subdivided into a plurality of square or rectangular subgroups of segments (2.2), each including at least one segment (2.2).
 6. The device of claim 5, characterized in that each segment (2.2) adjoins one adhesive strip (4) or further adhesive strips (4′), which cover connection lines.
 7. The device of one of claims 3-6, characterized in that for introducing the liquid crystal, a peripheral adhesive strip (4) is interrupted in the region of an adhesive strip (4′) meeting it at a right angle; and each thus-formed introduction opening (7) leads to two subsidiary regions located side by side. 